Acid Purification

Ordinary glucose is ct-glucopyranose monohydrate m.p. 80-85°C and [ajp 4-113-4 . In solution it gives a mixture with the form with [alo 4-52-5 . It is manufactured from starch by hydrolysis with mineral acids, purification and crystallization, and is widely used in the confectionery and other food industries. It is about 70% as sweet as sucrose. 

Although acetic acid and water are not beheved to form an azeotrope, acetic acid is hard to separate from aqueous mixtures. Because a number of common hydrocarbons such as heptane or isooctane form azeotropes with formic acid, one of these hydrocarbons can be added to the reactor oxidate permitting separation of formic acid. Water is decanted in a separator from the condensate. Much greater quantities of formic acid are produced from naphtha than from butane, hence formic acid recovery is more extensive in such plants. Through judicious recycling of the less desirable oxygenates, nearly all major impurities can be oxidized to acetic acid. Final acetic acid purification follows much the same treatments as are used in acetaldehyde oxidation. Acid quahty equivalent to the best analytical grade can be produced in tank car quantities without difficulties. 

The bottoms from the solvent recovery (or a2eotropic dehydration column) are fed to the foremns column where acetic acid, some acryflc acid, and final traces of water are removed overhead. The overhead mixture is sent to an acetic acid purification column where a technical grade of acetic acid suitable for ester manufacture is recovered as a by-product. The bottoms from the acetic acid recovery column are recycled to the reflux to the foremns column. The bottoms from the foremns column are fed to the product column where the glacial acryflc acid of commerce is taken overhead. Bottoms from the product column are stripped to recover acryflc acid values and the high boilers are burned. The principal losses of acryflc acid in this process are to the aqueous raffinate and to the aqueous layer from the dehydration column and to dimeri2ation of acryflc acid to 3-acryloxypropionic acid. If necessary, the product column bottoms stripper may include provision for a short-contact-time cracker to crack this dimer back to acryflc acid (60). 

Simplicity of production, high analysis, and excellent agronomic quaUty are reasons for the sustained high production and consumption of TSP. A contributing factor is that manufacture of the triple superphosphate has been an outlet for so-called sludge acid, the highly impure phosphoric acid obtained as a by-product of normal acid purification. 

Merthiolate/T4- )4-< 7 (3), sodium ethyLmercurithiosahcylate, known also as thimersol, is prepared from a 1 1 ratio of ethyhnercuric chloride/7(97-27-. and disodium thiosahcylate ia ethanol. After removal of the sodium chloride by filtration, the free acid is precipitated by acidification with dilute sulfuric acid. Purification is achieved by recrystallization from 95% ethanol, and the product, merthiolate, is obtained by neutralization with a stoichiometric amount of sodium hydroxide. 

Modem commercial wet-acid purification processes (see Fig. 4) are based on solvents such as C to Cg alcohols, ethers, ketones, amines, and phosphate esters (10—12). Organic-phase extraction of phosphoric acid is accompHshed in one or more extraction columns or, less frequently, in a series of countercurrent mixer—settlers. Generally, 60—75% of the feed acid P2 s content is extracted into the organic phase as H PO. The residual phosphoric acid phase (raffinate), containing 25—40% of the original P2O5 value, is typically used for fertilizer manufacture such as triple superphosphate. For this reason, wet-acid purification units are almost always located within or next to fertilizer complexes. 

Industry consolidation and rationalization have resulted. A shift in production toward wet-acid purification routes has occurred and only the most economically viable elemental phosphoms and thermal acid producers remain in business. There has also been an increased focus on higher value ... 

Analytical and Laboratory Operations. Sulfamic acid has been recommended as a reference standard in acidimetry (55). It can be purified by recrystaUization to give a stable product that is 99.95 wt % pure. The reaction with nitrite as used in the sulfamic acid analytical method has also been adapted for determination of nitrites with the acid as the reagent. This reaction is used commercially in other systems for removal of nitrous acid impurities, eg, in sulfuric and hydrochloric acid purification operations. 

Production of cyanohydrins is accompHshed through the base-cataly2ed combination of hydrogen cyanide and the carbonyl compound in a solvent, usually the cyanohydrin itself (17). The reaction is carried out at high dilution of the feeds, at 10—15°C, and pH 6.5—7.5. The product is continuously removed from the reaction 2one, cooled to push the equilibrium toward cyanohydrin formation, and then stabili2ed with mineral acid. Purification is usually effected by distillation. 

Because of their zwitterionic nature, amino acids are generally soluble in water. Their solubility in organic solvents rises as the fat-soluble portion of the molecule increases. The likeliest impurities are traces of salts, heavy metal ions, proteins and other amino acids. Purification of these is usually easy, by recrystallisation from water or ethanol/water mixtures. The amino acid is dissolved in the boiling solvent, decolorised if necessary by boiling with Ig of acid-washed charcoal/lOOg amino acid, then filtered hot, chilled, and set aside for several hours to crystallise. The crystals are filtered off, washed with ethanol, then ether, and dried. 

Classical gel electrophoresis has been used extensively for protein and nucleic acid purification and characterization [9, 10], but has not been used routinely for small molecule separations, other than for polypeptides. A comparison between TLC and electrophoresis reveals that while detection is usually accomplished off-line in both electrophoretic and TLC methods, the analyte remains localized in the TLC bed and the mobile phase is immediately removed subsequent to chromatographic development. In contrast, in gel electrophoresis, the gel matrix serves primarily as an anti-... 

Pure /7-toluenefulsonic acid Purification of / -Ts with BuOAc at 38-85 °C 164... 

Purification of industrial oils, kerosene/jet fuel, lubricating oils Mono- dicumyldiphenylamine Mono- dioctyldiphenylamine Dimer fatty acids Purification of xylenes Improvement of bromine number of recycle cumene in phenol plants Improvement of bromine number of recycle ethylbenzene in styrene plants based on liquid pha.se oxidation Alkylation of xylenes with diisobutylenes to mono-/ rr-butyI derivatives Phenyl xylyl ethane... 

This company founded in 1994, is a contract molecular biology and screening service company for the pharmaceutical, research, and clinical markets worldwide. Custom services include gene synthesis, DNA sequencing, site-directed mutagenesis, nucleic acid purification, and genotype/genetic analysis. 

A prerequisite step to any rDNA work is the initial isolation of DNA or RNA from the source material (which can be microbial, plant, animal or viral). Numerous methodologies have been developed to achieve nucleic acid purification, and some of these methodologies have been adapted for use in a variety of commercially available purification kits. Although details vary, the general... 

Undecenoic acid, 32, 104 M-Undecyl fluoride, 36, 42 10-Undecynoic acid, 32,104 a,/3-Unsaturated acids, purification of,... 

Double-lined kraft (DLK), 16 96 Double-lined landfills, 25 877 Double mashing, 3 577 Double-neutralization phosphoric acid purification, 13 824-825 Double polarization, in sugar analysis, 23 474... 

Table 12.6 contains, in a simplified way, the composition, location, and treatment of main thorium ores. The purification of thorium by TBP extraction is illustrated in Fig. 12.4. This purification takes place after the dissolution of Th in nitric acid, generally from a hydroxide cake. When the Th is dissolved in sulfuric acid, purification is achieved by extraction with long-chain alkylamines. 

Iso-Trioil Resulting from Nitric Acid Purification of Crude TNT , PATR-DB-TR 16-58 (Jan 1959)... 

Usually the gas is water-quenched to remove solids and tars. Ammonia, HCN, H2S dissolve in the water and high -content gas at high pressure may produce some formic acid. Purification of quench water contributes secondary Claus feeds, as will be seen. 

Spent acid and that from the absorption towers is distilled over sulphuric acid. Purification. Crude cyclonite consists of crystals of various sizes. They still contain 0.1-0.2% of nitric acid. For purification a suspension of cyclonite in water... 

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